NEW YORK (AP) _ Madison Avenue's celebration of the end of the Persian Gulf War is in full swing, but it could be a short party.

Military service advertising, one of the first casualties of the war, is back with patriotic pitches from the Army and Marines. The travel industry is campaigning to get business people and tourists moving again.

Saudi Arabia is said to be planning to spend $20 million over the next two months on ads thanking Americans for their help in ending the Iraqi occupation of Kuwait, though there's been no official word from the key U.S. ally.

Whether the postwar advertising euphoria is short-lived or a harbinger of healthier times is unclear.

Many advertisers say they have not increased ad spending plans even though U.S.-led multinational forces have quickly driven Iraqi troops into submission.

Joseph Ostrow, corporate media director at the ad agency Foote Cone & Belding, said many companies who kept their commercials out of extended war coverage are simply relocating the ads in other shows and spending the same.

The appearance of a number of ads saluting the troops should not be read as an indication that spending trends have picked up.

''It's too soon to really tell,'' he said.

Nonetheless, the flurry of postwar ads is welcome in the recession-pinched media industry. Forecasts are that 1991 ad spending will grow at the most sluggish pace in more than two decades.

The Army and Marines each suspended advertising as soon as the bullets started flying with the allied strike on Jan. 17 in Iraq and Kuwait.

But both services were back on network television this past weekend during college basketball games with commercials that saluted the troops.

The Army ran a commercial called ''Count on Me'' that showed troops training in a variety of settings.

''There was no sales message,'' said Col. John Myers, director of advertising for the Army Recruiting Command at Fort Sheridan near Chicago.

''We wanted to affirm the fact the Army has served well in the desert and is prepared to support the American national interests and the American people in the future,'' he said.

Myers said the Army probably won't resume recruitment advertising touting benefits such as career training and money for college until late this summer because of budget constraints. In the meantime, he said the Army has met if not exceeded its recruitment goals despite the gulf crisis.

The Marines had planned to be back on network television this past weekend regardless of the status of the war, said spokesman Major Rick DeChaineau. The ad showed still photos of Marines on historic occasions but, like the Army ad, had nothing specifically from the gulf.

The end of the war has led to formation of an unusual coalition of airlines, hoteliers, car rental agencies, attraction operators and travel agents at the suggestion of Commerce Secretary Robert Mosbacher. The group is headed by J.W. Marriott Jr., head of the hotel company that bears his name.

It plans to spend as much as $10 million for a six-week campaign to encourage travel now that the war is over, said Roger Conner, a spokesman for Marriott. It will include up to $5 million for advertising, he said.